ZF Friedrichshafen AG and Levant Power Corp., a Woburn, Massachusetts technology company spun off from MIT, have announced what they call the first fully active suspension system that includes a regenerative function that recovers energy from the motion of the suspension. The system is branded GenShock. Active suspensions are not new, General Motors experimented with an actively suspended ZR-1 Corvette when the automaker owned Lotus, which had worked with active suspensions before the technology was banned in Formula One. Going back even farther, there were the hydropneumatic Citroens and the last true Packards’ “torsion level” suspension. With road cars the goal in using such a system would be to combine good ride with good handling, soft sometimes and stiff sometimes, depending on the driving circumstances. Early tries at developing what chassis engineers call a “high bandwidth active suspension”, capable of dealing with those varying circumstances, have run into cost, complexity and power consumption issues. The GenShock system is claimed to be affordable, simple to integrate in existing suspension designs, and not only have modest power consumption but also be able to recover energy from the suspension.

The heart of the system is what Levant Power calls the Activalve TM, a device that combines electric and hydraulic motors (the companies are calling that an “electrohydraulic gear pump”) and can be adapting to standard mono, twin, and tri-tube damper configurations. Hydraulic fluid in the shock absorber is routed from the damper body through the valve, where the electric motor can be used to control the flow of fluid through the gear pump, or alternatively, the pump can be used to drive the electric motor as a generator, recovering electricity. The poorer the road quality, the more bumps there are, the more energy is recovered. Electronic controls adapt the damping characteristics to the driving situation, reducing body pitch and roll during cornering and braking. While the system adds a little bit of weight, compared to a passive suspension, it also eliminates the need to carry a jack, since the system is capable of raising or lowering each wheel independently.

Note that this is not a perpetual motion machine, like putting a wind generator on a car. It creates no new load on the powertrain, it merely recovers energy that would normally be turned into heat. ZF and Levant Power haven’t released any figures on just how much energy is recovered and whether that exceeds the power required to run the system. Like Innowatech‘s piezoelectric roadways, BMW’s Turbosteamer concept, or Purdue professor Xianfan Xu’s work recovering electricity from engine exhaust using large scale Peltier devices, the GenShock is harvesting energy that would otherwise go to waste.

That’s not to say that it isn’t a cool idea, and will be way simpler to integrate than a system such as Mercedes’ active body control which has many expensive parts, as well as a huge pump that puts a large drag on the motor.

Agreed. ZF is an innovative company and this is pretty cool. I envision a gas economy estimation gauge on the car dashboard that will jump in mpg every time you go over a pothole or railroad tracks. Ha!!!

Brake regenerating alternators have a clutch that releases it to spin freely when it gives the shot of kinetic energy to the battery (or capacitor if it’s a Mazda car), so it does not put a load on the engine for those few seconds – helping your mpg. I can see the energy recovered from the bumpy roads getting transferred to the battery and allowing the alternator clutch to let it spin freely.

I have a brake energy regenerating alternator in my car and you really do see the mpg meter jump when you start to brake. How much it actually helps the mpg when the alternator spins freely is still really a question to me, because it only happens for a few seconds.

A few years ago, I saw a video on a prototype suspension system from Bose, yes the audio equipment company, it used magnets and noise cancelling principles to achieve a very smooth ride.
I cannot look for the link on you tube for the video from here but it must be somewhere.
The car even jumped by itself if they want to.

I’d be shocked (no pun intended) if there weren’t a significant tie-in with the Bose system or the engineers who worked on it. Levant’s acting VP of engineering worked at Bose, and of course Amar Bose was on the MIT faculty for ages. (In fact, he donated a majority, non-voting stake of the company to MIT in 2011.)

I remember reading about that in Motor Trend several years back, where a 1992 Lexus LS could pull skidpad #s in the .9s, yet be as floaty as any of Detroit’s ’70s cruisers on the freeway!

Might be nice to see if such a system could help to mitigate disadvantages of certain suspension setups, such as when Honda went to struts instead of multi-link wishbones on the front of the new Accord. Don’t get me wrong, the Accord is still better than anything but the Mazda 6 and Fusion in the class in terms of handling, but a little of the “crispness” is lost. (The EPS doesn’t help either, though it’s better than early attempts at those systems in other vehicles.)

I could see Mazda really being into this. Their iEloop system is all about realizing the maximum mileage possible without making the leap to Hybridization. And it goes without saying that they’d be down with the ride and handling benefits.

The Mazda iEloop is just alternator brake regeneration going to a capacitor instead of a battery. Companies like Toyota, Ford, Mitsubishi, BMW and others have been using special brake regeneration alternators in their vehicles for years.

The Q45a was a hydraulic system of actuators and valves for each wheel with a conventional coil for rebound. When fully functional, it gave a very impressive highway ride but was hard to keep running as the system aged and there were few techs who really understood how the system worked well enough to keep them on the road.

Because the system carried a penalty in weight (150 lbs with the coil included) and horsepower (approx 30hp to run the pump system), most systems were retrofitted to use conventional shocks and coils once the system was inoperative.

The problem with these active suspensions is that they almost all end up being very costly to repair. The active components typically cost many times what a passive component costs. When the car goes out of warranty the only practical repair option is to replace the active components with passive…assuming the manufacturer built the car to accept passive components.

I have an old Cadillac Seville that came from the factory with a self adjusting suspension. Solenoids would automatically twist a valve at top of struts/shocks to dial-in the correct suspension damping according to speed and other variables. When this auto-adjusting suspension went bad I replaced the failed struts/shocks with passive components. The active struts cost over $500 a piece. The passive struts were less than $100

I would only consider a car with active suspension if I was certain I would be replacing the car before the warranty period was up. I would also be very leery of buying a used car with active suspension if there was no warranty.

I read all the negativity, and I remember my friends who would not buy a car with an automatic transmission because “it would break”. Also, a friend that would not buy a car with electronic ignition because “it would break”. You can be sure that if this active suspension system is put into mass production, it will be OK. If not the first iteration, by the time it works down to mass market vehicles, it will be OK. The same with electric cars. The first generation cars are not practical. The early adopters pay the price for buying early. People who wait, get the perfected product. But, without the early adopters, there would be no perfected product. Just because you would not buy it, does not mean that it should not be produced.

Now I’m no electrical engineer, but couldn’t you make the bumps in the road produce electricity with just some sort of piezo electrical material between the spring and the perch on all 4 corners? Sure it wouldn’t produce as much power as something like this, but it would cause no problems when/if it failed and could be implemented for a few bucks on any car.